检索结果-南通市图书馆

Hereditary effect of Al-based modifiers and grain refiners on structure and properties of A356.2 alloys

在线全文

学校读者我要写书评

暂无评论

中国有色金属学会会刊：英文版 2002年第2期12卷 233-237页

作者：李培杰张燕飞 V.I.Nikitin E.g.Kandalova K.V.Nikitin Department of Mechanical Engineering Tsinghua UniversityBeijing 100084China Physical and Technological Department Samara State Technical UniversitySamara 443010Russia

The hereditary effect of Al Ti, Al Ti B, Al Sr master alloys on the structure and properties of A356.2 alloys was investigated, and comparison analysis between the master alloys used in the foundry industry and the fine crystalline grain refiners produced by technologies of Samara State Technical University was conducted. The results show that less than 0.5% additions of FCR master alloys can promote 8%～20% in the elongation of as cast A356.2 alloys. FCR additives are more efficient in comparison with conventional grain refiners and modifiers. Their effectiveness depends on their genetic effect of their finer structures.

关键词：中间合金遗传效应晶粒细化 A356.2合金铝合金

Characterization,spectroscopic investigation of defects by positron annihilation,and possible application of synthesized PbO nanoparticles

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2021年第2期30卷 400-407页

作者： Sk Irsad Ali Anjan Das Apoorva Agrawal Shubharaj Mukherjee Maudud Ahmed P M g Nambissan Samiran Mandal Atis Chandra Mandal Department of Physics University of BurdwanGolapbagBurdwan 713104West BengalIndia Department of Physics A.P.C.Roy Government CollegeSiliguriDarjeeling 734010West BengalIndia Applied Nuclear Physics Division Saha Institute of Nuclear Physics1/AF BidhannagarKolkata 700064India Department of Physics Government General Degree College at PedongKalimpong 734311West BengalIndia

Nanocrystalline samples of highly pure lead oxide were prepared by the sol-gel route of synthesis.X-ray diffraction and transmission electron microscopic techniques confirmed the nanocrystallinity of the samples,and the average sizes of the crystallites were found within 20 nm to 35 *** nanocrystallites exhibited specific anomalous properties,among which a prominent one is the increased lattice parameters and unit cell *** optical band gaps also increased when the nanocrystallites became smaller in *** latter aspect is attributable to the onset of quantum confinement effects,as seen in a few other metal oxide *** annihilation was employed to study the vacancy type defects,which were abundant in the samples and played crucial roles in modulating their *** defect concentrations were significantly larger in the samples of smaller crystallite *** results suggested the feasibility of tailoring the properties of lead oxide nanocrystallites for technological applications,such as using lead oxide nanoparticles in batteries for better performance in discharge rate and *** also provided the physical insight into the structural build-up process when crystallites were formed with a finite number of atoms,whose distributions were governed by the site stabilization energy.

关键词： lead oxide nanocrystals positron annihilation sol-gel processes

Dual-ionic imidazolium salts to promote synthesis of cyclic carbonates at atmospheric pressure

在线全文

学校读者我要写书评

暂无评论

green Energy & Environment 2022年第6期7卷 1327-1339页

作者： Tengfei Wang Danning Zheng Beibei An Yi Liu Tiegang Ren HansÅgren Li Wang Jinglai Zhang Mårten S.g.Ahlquist Henan Engineering Research Center of green Anticorrosion Technology for Magnesium Alloys Henan UniversityKaifengHenan475004China Henan Engineering Research Center of Corrosion and Protection for Magnesium Alloys Henan UniversityKaifengHenan475004China College of Chemistry and Chemical Engineering Henan UniversityKaifengHenan475004China Department of Theoretical Chemistry&Biology School of BiotechnologyKTH Royal Institute of Technology10691 StockholmSweden

Novel dual-ionic imidazolium salts are shown to display excellent catalytic activity for cycloaddition of carbon dioxide and epoxides under room temperature and atmospheric pressure(0.1 MPa)without any solvent and co-catalyst leading to 96.1%product *** can be reused five times to keep the product yield over 90%.These intriguing results are attributed to a new reaction mechanism,which is supported by theoretical calculations along with the measurements of ^(13)C NMR spectrum and Fourier transform infrared spectroscopy(FT-IR).The excellent catalytic activity can be traced to a CO_(2)-philic group along with an electrophilic hydrogen *** work shows that incorporation of CO_(2)-philic group is an feasible pathway to develop the new efficient ionic liquids.

关键词： Dual-ionic imidazolium salts CO_(2)-Philic group New mechanism Room temperature Atmospheric pressure

Correlations between structure,microstructure,density and dielectric properties of the lead-free ferroelectrics Bi_(0.5)(Na,K)_(0.5)TiO_(3)

在线全文

学校读者我要写书评

暂无评论

Journal of Advanced Dielectrics 2015年第4期5卷 10-15页

作者： K.Anjali T.g.Ajithkumar P.A.Joy Physical and Materials Chemistry Division Central NMR Facility Academy of Scientific and Innovative Research(AcSIR)CSIR-National Chemical Laboratory(CSIR-NCL)Pune 411008 India

Solid solutions of the lead-free ferroelectric oxides Bi_(0.5)Na_(0.5)TiO_(3)(BNT)and Bi_(0.5)Na_(0.5)TiO_(3)(BKT),represented as(1-x)BNT-xBKT,are studied for very close compositions in the range0≤x≤0.36 to understand the correlation between the structure and the *** are varied in steps of △x=0.02 in the range0≤x≤0.1 and0.2≤x≤0.36 and△x=0.01 in the range 0.1≤x≤0.2,to precisely locate the structural transition as well as the morphotropic phase boundary(MPB)region and the compositional region of best *** refinement analysis of the powder X-ray diffraction patterns showed monoclinic phase up to x=0.17 and a mixture of monoclinic and tetragonal phases for x>***,the density and the dielectric constant showed linear variation up to x=0.17 and a large increase above this composition,showing maximum values in the compositional range 0.22≤x≤0.26,corresponding to the MPB *** features also showed corresponding changes,indicating close relationship between the structure,microstructure and properties of the different compositions.

关键词： Bismuth sodium potassium titanate Bi_(0.5)N_(0.5-x)KxTiO_(3) lead-free ferroelectrics morphotropic phase boundary structure-property correlations

Identification of Arceuthobium globosum using unmanned aerial vehicle images in a high mountain forest of central Mexico

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Forestry Research 2020年第5期31卷 1759-1771页

作者： Luis A.Leon-Banuelos Angel R.Endara-Agramont William gomez-Demetrio Carlos g.Martınez-garcıa E.gabino Nava-Bernal 50000 TolucaMexicoMexico

The identification of forests infested by parasitic plants is important for the design of appropriate control and prevention *** images and geographic information systems are commonly used to analyze the presence of pest and parasitic plants in the *** there is a need for finer *** the last decade,the use of unmanned aerial vehicles has become increasingly common for capturing aerial images(gB values(Red,green and Blue)through the colorimetric ranges for use in identification of Yellow Dwarf Mistletoe(YDM)(Arceuthobium globosum)in aerial images taken in a forest of central Mexico via a programmed *** tonalities of YDM were classified according to its phenological stages,***(young stage),yellow(adult stage),and brown(senescence stage),considering two light intensities,sunny and ***-parametric tests were used in statistical *** Spearman test showed significant negative correlation(pgical stage and colour,indicating that lower RgB values were associated with greater *** differences between groups were analysed using Kruskal–Wallis(pgorithm identified the presence and predominant colours of YDM according to its phenological stage.

关键词： Colorimetric analysis RgB Pinus hartweggi Parasitic plants Remote sensing

A strong and ductile NiCoCr-based medium-entropy alloy strengthened by coherent nanoparticles with superb thermal-stability

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2023年第1期132卷 201-212页

作者： D.D.Zhang J.Kuang H.Xue J.Y.Zhang g.Liu J.Sun State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an 710049China

In this work,we designed a novel NiCoCr-based medium-entropy alloy(MEA)strengthened by coher-ent L12-nanoparticles,i.e.,(NiCoCr)92 Al 6 Ta 2(at.%).The strengthening and deformation mechanisms of the material and the coarsening kinetics of the coherent precipitates were systematically *** results indicated that giant precipitation hardening and its synergy with other strengthening contributors confer on the aged material a yield strength as high as 1.0 ***,a unique particle-features-dependent plasticity mechanism was revealed in this *** is,the alloy with a lower volume frac-tion,denser distribution,and finer particles mainly deformed by dislocation planar slip,otherwise,stack-faults-mediated plasticity was favored,rationalized by the cooperative/competitive effect of stack-fault energy,spatial confinement,and applied ***,the coarsening behavior of precipitate fol-lowed a modified Lifshitz-Slyozov-Wagner(LSW)model,and the nanoparticles displayed remarkably su-perior thermal stability compared to most traditional superalloys and reported multicomponent *** superb coarsening resistance of precipitate originated from the coupled effect of intrinsic sluggish diffusion in multi-principal alloys and the dual-roles of Ta species as a precipitate *** work provides a new pathway to develop strong-yet-ductile multicomponent alloys as promising candidates for high-temperature applications.

关键词： Medium-entropy alloy Mechanical properties Precipitation hardening Deformation mechanisms Coarsening kinetics

Effect of Applied Pressure on the Joining of Combustion Synthesized Ni_3Al Intermetallics with Al Alloy

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2008年第1期24卷 123-126页

作者： g.S.Cho J.H.Yang K.H.Choe K.W.Lee A.Ikenaga Advanced Material Processing Team Korea Institute of Industrial Technology 7-47 Songdo-Dong Yeonsu-Ku Incheon 406-840 Korea Department of Metallurgy and Materials Science Graduate School of Engineering Osaka Prefecture University 1-1 Gakuen-Cho Sakai Osaka 599-8531 Japan

We focused on the surface reinforcement of ligth weight casting alloys with Ni-AI intermetallic compounds by in-situ combustion reaction to improve the surface properties of non-ferrous casting *** our previous works,green compact of elemental Ni and Al powders were reacted to form Ni-3Al intermetallic compound by SHS （Self-propagating high temperature synthesis） reaction with the heat of molten Al alloy and simultaneously bonded with Al casting *** some defects such as tiny cracks and porosities were remained in the reacted *** we applied pressure to prevent thermal cracks and fill up the pores with liquid Al alloy by squeeze casting *** compressed Al alloy bonded with the Ni-3Al intermetallic compound was sectioned and observed by optical microscopy and scanning electron microscopy （SEM）.The stoichiometric compositions of the intermetallics formed around the bonded interface and in the reacted compact were identified by energy dispersive spectroscopy （EDS） and electron probe micro analysis （EPMA）. Si rich layer was formed on the Al alloy side near the bonded interface by the sequential solidification of Al *** porosities observed in the reacted Ni-3Al compact were filled up with the liquid AI *** Si particles from the molten Al alloy were detected in the pores of reacted Ni-3Al intermetallic *** Al casting alloy and Ni-3Al intermetallic compound were joined very soundly by applying pressure to the liquid Al alloy.

关键词： Joining Combustion synthesis Ni3AI Intermetallic compound Squeeze casting

Vleiotic recombination and male infertility： from basic science to clinical reality？

在线全文

学校读者我要写书评

暂无评论

Asian Journal of Andrology 2011年第2期13卷 212-218页

作者： Michael Chann Patricio E Lau Helen g Tempest Department of Human and Molecular genetics Herbert Wertheim College of Medicine Florida International University Miami FL 33199 USA

Infertility is a common problem that affects approximately 15% of the population. Although many advances have been made in the treatment of infertility, the molecular and genetic causes of male infertility remain largely elusive. This review will present a summary of our current knowledge on the genetic origin of male infertility and the key events of male meiosis. It focuses on chromosome synapsis and meiotic recombination and the problems that arise when errors in these processes occur, specifically meiotic arrest and chromosome aneuploidy, the leading cause of pregnancy loss in humans. In addition, meiosis-specific candidate genes will be discussed, including a discussion on why we have been largely unsuccessful at identifying disease-causing mutations in infertile men. Finally clinical applications of sperm aneuploidy screening will be touched upon along with future prospective clinical tests to better characterize male infertility in a move towards personalized medicine.

关键词： fluorescent in situ hybridization immunofluorescence male infertility meiotic recombination semen parameters synap-tonemal complex

Diastolic heart failure in the elderly

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of geriatric Cardiology 2006年第4期3卷 210-221页

作者： Jeffrey H.Barsuk William g.Cotts Division of general Internal Medicine Section of Hospital Medicine Department of MedicineNorthwestern University Feinberg School of MedicineILUSA Division of Cardiology Center for Heart Failure Northwestern University Feinberg School of MedicineILUSA

Heart failure with preserved left ventricular function is a common problem among elderly patients. given that diastolic heart failure (DHF) occurs in up to 50% of all heart failure admissions, and that incidence increases with age, knowledge of current recommendations for its diagnosis and treatment are extremely important for the elderly population. Causes of DHF include the aging process itself, hypertension, left ventricular hypertrophy, aortic stenosis, and hypertrophic obstructive cardiomyopathy. The patient with DHF may present with signs and symptoms similar to those observed in systolic heart failure. Treatment goals for the patient with DHF include achieving normal volume status, improving relaxation of the left ventricle, regression of hypertrophy if possible, and management of any co-morbidities that may aggravate the clinical status of patients with DHF. Hopefully, in the future, further data from randomized clinical trials will allow a more defined approach to care in these patients.

关键词： diastolic dysfunction elderly heart failure left ventricular hypertrophy aging